The present invention is directed to an arrangement for synchronization of radio transmission in a radiotelephone subscriber connection network for connection to a telecommunication exchange.
What is accordingly involved is the synchronization in a radiotelephone subscriber connection network that has a central unit serving for the control of the radiotelephone system, a least one decentralized concentrating unit, as well as a plurality of base stations connected to these decentralized units via a U-interface, the radio transmission ensuing between the base stations and subscriber stations.
In a radiotelephone subscriber connection network that operates according to the DECT standard (Digital European Cordless Telecommunication), there is a multi-cellular structure, that is, each of the base stations forms the center of a proper cell, whereby the coverage of these base station cells and the spatial arrangement of the base stations are selected such that an overall region is covered gap-free. When the individual base stations do not operate synchronously, interference arises at the boundaries of the cells, overlaps being unavoidable thereat, with the consequence that the spectral efficiency, that is, the possibility of multiple utilization of one and the same frequency for different connections, is reduced. There is therefore particular interest in a synchronization of the operation of the base stations.
It is also provided according to the DECT standard that the mobile terminal equipment that are in radio communication with the base stations constantly check the quality of the radio channel employed during an existing connection and additionally check the quality of all other, free radio channels. Also, a change of channels (which should occur completely unnoticed) is initiated using the base stations when one of the remaining free channels has better quality than the channel used at the moment. Such a "handover" can also ensue in such a way that a channel switch occurs from a channel of the cell of a first base station to a channel of the cell of a neighboring base station. In this case, it must be assumed that the base stations also work time-synchronized in view of an interruption free handover.